S&P affirmed Westlake's corporate credit rating at triple-B-minus, one notch into investment grade. The outlook is now stable.

S&P noted Westlake benefits from a fair degree of manufacturing integration in its businesses and a favorable domestic market share in a key product, low-density polyethylene.

S&P's move comes a day after Fitch Ratings Services removed Westlake's ratings on watch for a possible downgrade. Fitch also rates Westlake at triple-B-minus.

S&P and Fitch had both placed Westlake's ratings on watch in January when the company unveiled an unsolicited $1.03 billion cash offer for Georgia Gulf. Westlake in February increased its acquisition offer by 17%, to $35 a share, but Georgia Gulf said the offer undervalued the company.

Westlake, a maker of basic chemicals, vinyls, polymers and fabricated PVC products, said Friday it has no plans to pursue a future transaction for Georgia Gulf. Following confidential discussions between the two companies, Westlake said it would walk away from its planned deal and will sell all its stock in Georgia Gulf.

Shares slid 2.4%, to $56.10 in recent trading. The stock is up 39% since the start of the year.

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